NUNATAK AND CASCADING GLACIERS 145
the edge of the hanging valley (PL LXXI), then tumbles precipitously down the slope in a shallow gorge (PL LX, B), which it is actively deepening. In the earlier stages of destruction of a cascading glacier the drainage is less concentrated, and when we reach as early a stage as that of the Cascading Glacier itself, a multitude of streams discharge the ice drainage down the steepened slope in no well defined courses.
This cascading type of glacier, exists, to some extent at least, in the Alps, and, in fact, must be a common condition in the recession of trunk glaciers. Doubtless it was far more common, and far better developed in the Alps during the greatly expanded condition of glaciers in the Glacial Period; for the Alpine glaciation of that time more closely resembled the glaciation in Alaska to-day than does the system of present-day Alpine glaciers.